This invention relates to an automatically retractable stop apparatus that is used to position metal parts on the table of a conventional machine tool. More particularly, this invention relates to a spring loaded positioning stop that automatically retracts after the part is positioned so that the required machining operation can be successfully performed without damaging or disrupting the machine.
CNC milling machines and other widely available machine tools are currently used to perform various operations (e.g. cutting, shaping, drilling, and routing) upon a virtually endless assortment of metal parts or components. Before the machining operation is performed, the part to be machined must be properly positioned and held in place on the machining table. Standard table-top vises are used to hold the part in place; however, before the vise is locked, the part must be accurately positioned within the jaws of the vise. A number of conventional positioning stops are currently used to accomplish this task.
Typically, the positioning stops that are currently available are relatively simple, manually operated devices. The machinist installs the stop at a desired location on the table, sets a plate, arm or other stop component and engages the metal part to be machined against the stop component. The stop must then be disassembled and removed so that the desired machining operation may be completed.
Unfortunately, the known positioning stop devices present serious problems. The machine operator must remember to remove the stop before the machine tool is operated. Otherwise, there is a serious risk that the cutting head or other part performing the machining operation will strike the stop. This is likely to cause serious and expensive damage to the drill, cutter or other machine tool. Valuable time and manpower must then be expended to repair the machine. In many cases, the tool is subjected to extended and very expensive down time. Replacing damaged tools can cost hundreds if not thousands of dollars.
It is not at all uncommon for the machine tool operator to forget to remove the positioning stop. Oftentimes, the machining operation is being performed repetitiously in a tedious manner. Moreover, in CNC applications the machine must be properly programmed by the operator. This can distract the operator""s attention from the important task of removing the positioning stop before the cutter or other component is operated. Even when the machinist does remember to remove the positioning stop, this task must be performed manually. In situations were numerous parts must be machined, the positioning stop must be installed and removed for each and every part. This is tends to be an inefficient, time consuming, labor intensive and extremely tedious operation.
It is therefore an object of this invention to provide a positioning stop for machine tools which is automatically retractable so that the machining operation may be completed quickly and effectively without having to manually remove the positioning stop prior to each such operation.
It is a further object of this invention to provide an automatically retractable positioning stop for machining tables which virtually eliminates the expensive, time consuming and disruptive damage often caused when the positioning stop is inadvertently left in place during the machining operation.
It is a further object of this invention to provide an automatically retractable positioning stop for machining tables which permits metal parts to be positioned on a machining table quickly, conveniently and accurately without requiring the manual assembly and disassembly of the stop between each machining operation.
It is a further object of this invention to provide a positioning stop for machine tools which automatically retracts after a part is positioned on the machining table so that the machining operation may be completed quickly and conveniently without risking potentially expensive damage to the machine tool and resulting repairs, wasted worker time and machine down time.
This invention results from a realization that an automatically retractable positioning stop would enable a machine tool operator to perform his job much quicker and more efficiently because he would no longer be required to disassemble the stop prior to each separate machining operation.
This invention features an automatically retractable positioning stop for machining tables. The stop includes a base that is secured to the machining table at a predetermined position. A retractable stop component is mounted to the base for alternating between retracted and extended positions. Spring means are engaged with the stop component for urging the stop component into the retracted condition and for permitting the stop component to be manually urged into the extended condition. In the extended condition, the part to be machined may be engaged with the stop component and thereby positioned properly on the machining table. In the retracted condition, the stop component is held sufficiently clear of the part to be machined such that the machining operation may be performed without interference from the stop component. After the part to be machined is properly positioned in this manner, that part is locked in a standard table-top vise and the stop component is manually released so that the spring returns the stop component to the retracted condition.
In a preferred embodiment, the stop component includes an elongate stop arm or bar that is pivotably mounted to the base. More particularly, a pivot axle may be rotatably interengaged with a cylindrical bearing in the base. The stop bar may be secured to one end of the pivot axle on a first side of the base and a collar may be secured proximate the second end of the pivot axle on an opposite second side of the base. The base may include an interior annular race or recess that interengages the collar. The race may be disposed about the interior bearing of the base. A first spring retaining element may be mounted to the base within the race and a second spring retaining element may be mounted to the collar and extend within the race. The spring means may comprise a helical compression spring that is formed between the first and second spring retaining elements within the race. Alternatively, the spring may be received in an interior race or chamber within the collar.
An annular groove may be formed within the side of the base opposite the side that includes the spring retaining race. A first limit pin may be mounted within the base and positioned within the annular groove. The pivot axle may include on the first side of the base a drum that is interconnected to the stop bar. Second and third limit pins may be mounted within to the drum and extend within the annular groove. In the retracted condition, the spring urges the pivot axle to rotate within the central bearing of the base such that the stop bar is pivoted away from the part to be machined. In this position, a first one of the limit pins carried by the drum interengages the limit pin mounted to the base. Alternatively, when the pivot arm is rotated into the extended condition, the spring is compressed between these spring retaining elements in the race. At the same time, the second limit pin carried by the drum engages the limit pin fixed to the base. This limits pivoting of the stop arm into the extended condition. The stop bar is then held in this position until the part to be machined is properly positioned against the stop bar.